1. Field of the Invention
Embodiments of the present invention relates to filter compositions, formation surfaces including a filter composition of this invention, methods for forming a self-degradable filter cake, a self-degradable filter layer, or a plurality of self-degradable filter layers on surfaces of a formation or zone thereof, and systems including a well having zones including a self-degradable filter cake or filter layers of this invention, where the self-degradable filter layers include components that erode or dissolve without the need for a separate fluid treatment to cause erosion or dissolution.
More particularly, embodiments of the present invention relates to filter compositions, formation surfaces including a filter composition of this invention, methods for forming a filter cake, a filter layer, or a plurality of filter layers on formation surfaces of a formation or zone thereof, and systems including a well having zones including a filter cake or filter layers of this invention, where the filter compositions including one or more (one or a plurality of) erodible or dissolvable components and where the erodible or dissolvable components erode or dissolve without the need for a separate fluid treatment to cause erosion or dissolution.
2. Description of the Related Art
Correct placement of a chemical treatment such as sand or water control treatments is often complicated by the presence of largely varying permeability zones which are often seen in long horizontal wells. High permeability zones, in particular, may take a large portion of the treatment, leading to insufficient treatment of the rest of the formation. Certain prior filter cakes require a separate treatment to remove the filter cake which may lead to compatibility issues with the well treatments such as sand control treatment fluid or may increase the cost or complexity of the job. Furthermore, as the filter cake is removed, the uneven permeability of the formation may be re-established, leading to uneven coverage with the degradation treatment and thus incomplete filter cake dissolution. Dealing with high permeability “thief” zones has been typically achieved through the injection of particulate materials, foams, plugs, packers, or blocking polymers such as crosslinked gels. Particulate materials that have been pumped include waxes, naphthalene, oil-soluble resins, degradable polymers, and others materials as described more fully in U.S. Pat. Nos. 4,527,628A; 8,109,335B2; 3,724,549A; 3,302,719A; 4,005,753A and United States Published Application Nos. 20110005761A1 and 20120138303A1. These particulate systems are generally used to seal a high permeability zone after a treatment, which then diverts the next round of treatment away from that zone. This process is then applied again until treatment is complete.
As can be seen in the referenced patents, particulate diverting agents (both degradable and non-degradable) are known. However, in these cases, the diverting agent is used to seal a particular, high permeability portion of the formation so that other, lower permeability portions of the formation can be treated. This process can be repeated multiple times.
On the other hand, in this invention, pumping a filter composition of this invention will form a filter cake or filter layers across the entire formation. The filter cake or layer will have a controlled permeability that partially or substantially equalizes the effective formation permeability so that well treatments may be delivered to all formation zones equally with equal effectiveness. Therefore, the well treatment will actually occur through the filter cake or layer across the entire or a majority portion of a formation or zone or zones thereof, rather than the filter cake or layer being used to seal off segments of the formation and then divert away from them.